Ok, part of this is just that I really like the word “Glyptodon” and am trying to find more uses for it ;-). But there is a point here, I’m pretty sure.
A while back I was teaching a class, and the gentleman teaching before me, an Algonquin Native Descendent, who was talking about the history of the ways that waterways in the Northern US had impacted patterns of settlement and development, became quite passionate at the sight of Eric’s t-shirt, which had an mastodon on it. The gentleman launched into a staunch defense of his ancestors, who for a long time were typically considered to be the main culprits in the extinction of the North American mega-fauna, including the Mastodons and Mammoths.
The gentleman argued that his people were being maligned by scholars who have had insufficiently credited climate factors in the extinction of the animals, and claimed that his ancestors were not guilty. Since we’d expressed no opinion on the subject, we were a little surprised to see so passionate a defense, but his observation was that something very critical hinges on this question – and I think he’s right. If historically speaking there are few, or no societies in which humans have lived without basically destroying the creatures and environment around them, we can begin to take from that the idea that humans are inevitably destructive. Indeed, our history seems to support this idea – while new archaeological evidence suggests we were interbreeding with Neandertals, it also suggests that one of our early projects may have been the genocide of the other upright folks like us.
The gentleman in question argued quite forcefully, however, that while North American native people’s were hardly without impact – among other things, they heavily managed forests, rivers and prairies – that fundamentally their impact was much lower than is implied by the attribution of the megafauna extinctions to their credit. If that’s true, he argues, than we should begin to attribute the inability of humans to live sustainably less to an innate human-ness and more to particular types of human habitation and relationshp to their world.
Thus, I found it interesting to read a new study, published in _Evolution_ that suggests in fact that climate change really was a (it would be overstating things to say “the” – it isn’t clear that the gentleman’s ancestors are fully off the hook) primary driver in the extinction of the megafauna. Using this approach, the study’s authors suggest:
The study shows that climate change had a global influence over extinctions throughout the late quaternary, but the level of extinction seems to be related to each continent’s footprint of climate change. When comparing continents it can then be seen that in Africa, where the climate changed to a relatively lesser extent there were fewer extinctions. However, in North America, more species suffered extinction, as reflected by a greater degree of climate change.
A key piece of evidence in the humans versus climate debate is the size of the extinct mammals. It has always been assumed that humans mainly impacted on populations of large mammals, while if climate change played the key role there should be evidence of large impacts on small mammals as well as the larger animals.
The team’s results show that continents which suffered larger climate change impacts suffered larger extinctions of small mammals and viceversa, further strengthening the idea that climate change was a key factor in controlling past extinctions on a global scale.
This research has important implications for the current study of climate change, not only in revealing the role of the climate in causing extinction in mammals, but also by demonstrating how the effect will be different across regions and continents
I personally don’t really have a dog in this hunt – my ancestors both lived on the North American continent and did or did not eat the giant sloths, and lived in Europe and helped exterminate my other ancestors. My own genome is by no means straightforward enough to make it worth taking sides. Moreover, I’m not sure that we can have sufficient certainty on this subject to be able to make a case for a sustainable human history – or not. But if we could, wouldn’t that be interesting?